The present invention relates to vacuum cleaners and more particularly to an improved shop type vacuum cleaner.
Two main types of vacuum cleaners are known at present. The first type of vacuum cleaner, which is most wide spread, includes a flexible bag which is permeable to air and which is disposed in an airtight enclosure between a suction orifice and a suction device. Air sucked by the suction device flows through the wall of the flexible bag which then acts as a filter and retains the dirt contained in the sucked-in air. Such a vacuum cleaner is not suitable for sucking up a liquid since the liquid will flow through the pores of the flexible bag, nor can it be used with damp substances which would very quickly clog the pores of the flexible bag. Further, flexible bags are either made of cloth, in which case it is necessary to empty them out in order to reuse them which is a particularly disagreeable operation to perform, or else they are made of paper, in which case they are fragile and may tear while being handled which makes it necessary to clean out the vacuum cleaner itself and to vacuum up the dirt which has fallen onto the ground.
In the second type of vacuum cleaner, a rigid receptacle is disposed in an airtight enclosure with an opening facing the suction orifice, and the suction device is disposed in a side opposite to the opening. The air sucked by the suction device flows around the rigid receptacle while the dirt is projected, generally under gravity, into the rigid receptacle. Although such a vacuum cleaner is capable of picking up wet dirt and even liquids, it is still necessary to transfer the contents of the rigid receptacle into a garbage bin. Such a device is, therefore, unsuitable for vacuuming harmful particles or substances that redisperse in the atmosphere during the handling, such as asbestos for example.
Attempts have been made to dispose an airtight flexible bag in the rigid receptacle, but it has been observed that the bag is sucked into the suction device when the device is switched on, and as a result it is not possible to use an airtight flexible bag in existing vacuum cleaners.
In addition, it has been proposed to provide a negative-pressure collection system, for collecting refuge, such as debris, particulate matter, and the like comprising a doubled wall chamber arrangement wherein the outer wall is a solid wall and the inner wall spaced from the outer wall is perforated with a flexible bag being disposed adjacent the perforated wall. A suction or negative-pressured device is provided which supplies a negative-pressure in the space between the two walls and inside the flexible bag thereby maintaining the flexible bag against the perforated inner wall to thereby collect the debris or refuge as the matter is picked up by the negative pressure.